Lamps of the type to which the present invention relates--and as illustrated in FIG. 2A--are known. The lamps themselves have standardized bases, and the sockets must be adapted to fit these standard bases. The known socket is safe with respect to stray electrical fields, spurious discharges, or surface or creep paths.
Basically, the socket is of generally cylindrical construction. Connecting cables lead from the socket, to supply ignition as well as operating energy. The inner structure of the socket is essentially symmetrical and compact. Contacting elements adapted to connect with contacting blades, lugs or pins extending from the lamp element itself are retained within chambers of essentially H shape, so that the contacting elements are surrounded at all sides, open only through suitable openings to receive the connecting blades from the lamp and, at the other end, the cables extending from the socket. The overall combination of the system lamp--lamp base--socket is capable of withstanding high voltage pulses in the order of up to about 20 kV , required for reignition of the lamp when it is still hot.
The socket is assembled without use of rivets or any other metallic attachment parts. This substantially increases the high voltage protection. The contact elements are inserted into the associated chamber, when it is still open, and pre-assembled with the connecting cables which are threaded through a suitable cable opening. The chambers are then closed off by a cover plate or cover plates which, at the same time, locate the contact elements for the connecting blades of the lamp in position. These connecting blades pass through openings formed in the covers, matching the size and shape of the connecting blades or pins. This ensures introduction of the contact elements in appropriate form, and good contact with the connecting elements within the socket itself. The cover plates, as the socket itself, are made of an insulating material, for example ceramic, capable of accepting high temperature. Other materials may also be used. The cover plates are secured to the remainder of the socket structure by adhesives or cements above the chambers.
The cover plate is formed with a recess which fits around a complementary portion of the lamp base, so that an interfitting connection between the lamp base and the socket is ensured. This arrangement, by overlap of socket and the lamp base within the region of the plug connection, further increases the protection against inadvertent touching or engagement of extraneous elements, or of a careless operator, and further increases the path length protecting the electric energy carrying components against arc-over or spurious creep paths. The openings to receive the contact blades or pins extending from the lamp are located within this recess. The cover plates, adhered or cemented to the remainder of the socket, are partially covered by the lamp base, when the lamp is inserted therein, so that even if the adhesion or cementing of the socket should come loose, or have been incompletely cured, the cover plate cannot come loose from the socket, when the lamp is engaged therein. Thus, the electrical integrity and insulation is maintained, even in case of equipment malfunction.
The lamp base is formed with an extended portion which fits into the recess of the socket, to provide a mechanical interfit. This recess is provided with an axially projecting ridge or rib, which fits into a groove formed in the projection of the base, to ensure insertion of the lamp into the socket in a predetermined direction, to maintain the polarity of the lamp terminals. This is important for appropriate application of energy to the lamp, and especially the high voltage ignition pulse.
All constructional elements are located within the interior of the socket, and the socket has no externally accessible assembly joints, bores or the like. The smooth outer contour, with an integral wall, prevents high voltage flares.
The socket is particularly suitable for use with lamps of minimum dimension, that is, for example for lamps used in portable film and television camera and like applications, associated with a reflector and operated for example from battery power supply as used, for example, in live film or television reporting, where daylight-simulated auxiliary light is required. Usually, the lamp fixtures are small and, for portability and association with a camera, have to be light.
It has been found, in actual use, that the bases constructed in accordance with the aforementioned German Utility Model No. G 88 12 466, particularly when associated with hand-held reflectors, cannot accept at all times the mechanical stresses applied against the electrical terminal elements, when the sockets are installed in lamps which are handled carelessly. It has been found that, upon rough and inconsiderate handling of the fixtures, the contact elements within the chambers might tip and cause chatter or shift of the electrical terminal and contact engagement between the contact elements in the sockets and in the lamp base. The lamp socket may be aligned with an optical system, for example a reflector or a lens system, and upon relative shift of the socket and the lamp, adjustment of the lamp with respect to the fixture may change, hence changing the pattern of the light output.
It would be possible to secure the known contact elements within the socket chamber base by a cement. Doing so, however, is expensive and is difficult to carry out in automatic manufacturing machinery.